A variety of mattress designs having coil innerspring assemblies have been developed within the industry and have been in use for a number of years. Most of these innerspring mattresses were designed to have uniform firmness across their entire length and/or width, with each spring in the mattress exerting the same level of resistance for a given spring deformation.
In recent years, coil innerspring assemblies have been developed which provide the mattress with multiple sections having different degrees of firmness. The variation in firmness between mattress sections is often referred to as “posturized” or “posturization”. One example of a posturized coil innerspring assembly is described in U.S. Pat. No. 6,398,199 to Barber. As disclosed in the '199 patent, the weight of different regions of an individual's body can vary significantly (e.g., the head, torso and leg regions). As a result, the different regions of the body tend to exert different forces or loadings onto the corresponding sections of the mattress when the individual lies on the mattress in a prone position. For example, the head and leg regions of the body tend to exert less force or loading onto the mattress compared to the torso region of the body. To accommodate for this variation in loading, the coil innerspring assembly disclosed in the '199 patent is designed to provide the innerspring mattress with multiple sections or areas having different degrees of firmness or resistance to loading.
While advances have been made in the industry to provide an innerspring mattress having increased comfort, there is a continuing need to provide improved coil innerspring assemblies, particularly with regard to coil innerspring assemblies having a firmness which varies between initial loading of the mattress (e.g., when an individual first lies down on the mattress) and on-going loading of the mattress (e.g., continued support of the individual lying on the mattress).
Thus, there is a general need in the industry to provide an improved coil innerspring assembly having varying degrees of firmness. The present invention meets this need and provides other benefits and advantages in a novel and unobvious manner.